The invention relates to a friction vacuum pump, with a housing, a rotor and a rotor bearing which is supported in the housing via a sleeve-like support.
Gaede pumps (cylindrical rotor with a pumping slot and a barrier slot between inlet and outlet rotating in a housing), Holweck pumps (cylindrical rotor with spiral grooves on the stator or on the rotor rotating in a housing), Stegbahn pumps (rotating and fixed annular discs with spiral grooves) and turbomolecular pumps which are equipped with rotating and guiding blades, belong to the class of friction pumps. It is known to equip friction pumps with differently designed pumping sections.
The pumping characteristics of a friction pump depend chiefly on the distance between the active pumping surfaces which move relative to each other. The smaller the slot, the better in particular the compression of that friction pump will be. However, there are limits as to the minimum dimensions of the slot, since small oscillations of the rotor must be permitted. This applies particularly when passing through the range of resonance frequencies as the rotor runs up to its operating speed.
It is the task of the present invention to design, for a friction pump of the aforementioned kind, the support for the rotor bearing in the housing in such a way, that in spite of a support which permits oscillations of the rotating system, optimally small distances can be selected between the active pumping surfaces.